Mechanically controllable mortice locks utilise two hubs, each associated with a lever or other handle on each side of a door. They can be configured to provide any one only of four different pairs of functions when locked or unlocked, as follows:
(Pair 1) Unlocked function—door can be opened for entry or egress from either side without key. Locked function—door can be opened for entry without key but key needed for egress (i.e. by unlocking or by latch retracting/key over-riding without unlocking);
(Pair 2) Unlocked function—door can be opened for entry or egress from either side without key. Locked function—door can be opened for egress without key but key needed for entry;
(Pair 3) Unlocked function—door can be opened for entry or egress from either side without key. Locked function—key needed for entry and egress; or
(Pair 4) Unlocked function—door can be opened for entry or egress from either side without key. Locked function—door can be opened for entry or egress from either side without key (effectively creating a latch).
Configuring a lock in the desired one of the four above function pairs is known as handing the locking mechanism and allows the lock installer to ensure that the pair of functions best matches the requirement of a particular door. The ability to hand a lock: saves a lock manufacturer from having to make, stock and sell four different locks, one for each of the above four pairs of functions; saves a customer from having to know which parts to order for which door; and avoids an incorrectly handed lock from being delivered. These last two requirements can be particularly important when purchasing a large number of locks for installation in, for example, a multi-story building with many doors. Handing is done by adjusting or manipulating one or more of the lock's components.
A disadvantage of known mechanically controllable locks is that once the lock is handed (ie. the function that each side of the lock is able to offer is selected) the lock can only operate to offer that selected one pair of functions. Accordingly, if a first side of a lock is required to be free egress when the lock is locked and a second side of the lock is required to be locked when the lock is locked, then that first side can never be locked unless the lock is accessed and the handing changed. To do this the lock must be removed from the door (or otherwise physically accessed) to change the handing to a different one of the function pairs.
Electrically controllable mortice locks, which can be locked and unlocked with an electrical signal (ie. instead of a key) are also known. Such locks can similarly only be handed to provide one of the above pairs of functions. They also suffer from the disadvantage that the lock must be removed from the door (or otherwise physically accessed) to change the handing to different one of the function pairs.
However, in some mechanical and electrical lock installations, a change in the function of the lock is desirable or necessary without accessing the lock. For example, a door may require a business hours locked function of egress without key/signal but key/signal needed for entry and an after hours locked function of key/signal needed for entry and egress. As the handing can not be changed without removing/accessing the lock, such changes of functionality during normal use are not possible with any single existing lock. With mechanical mortice locks, such changes of functionality are achieved by installing a separate deadbolt on the same door for after hours use. With an electrical mortice lock, a separate electromagnetic lock is installed on the same door for after hours use. Both of these approaches have increased product and installation costs. The associated electrical systems also have increased system and control complexity.
Electrically controllable mortice locks must also be set to operate in either a fail safe condition, in which they lock a door when energised and unlock a door when de-energised, or a fail secure condition, in which they unlock a door when energised and lock a door when de-energised. This allows access through a door in the event of a power failure to be predetermined as allowed or prevented in accordance with safety and security requirements.
Known electrically controllable mortice locks can only be handed into one of the four handing function pairs described above. Further, such locks can only be set to fail safe to the unlocked function that has been selected for the door during handing or to fail secure to the locked function that has been selected for the door during handing. Accordingly, if a lock is set to fail secure and during normal operation (ie. power is available) a first side of the lock is required to be free egress when the lock is locked while a second side is required to be locked when the lock is locked, then that first side can never be locked during a power failure unless the lock is accessed and the handing (function pair) changed. Put another way, the locking of both sides can not be done.
For example, during normal operation (i.e. with power available) a door may require a locked function of egress without key/signal but key/signal needed for entry and a failsecure (ie. power failure) locked function on both sides of the door. As the handing can not be changed without removing/accessing the lock, such change of functionality is not practical with any existing electrical mortice lock. A separate, failsecure electromagnetic lock is installed on the same door for power failure conditions. This approach has increased product and installation costs. The electrical systems also have increased system and control complexity.